1. Technical Field
The present disclosure relates to thermal cyclers, and particularly to a thermal cycler based on carbon nanotubes.
2. Description of Related Art
The polymerase chain reaction (PCR) is a technique broadly utilized in the field of biology and, in particular, for genetic research and medical diagnosis. PCR is based on thermal cycling, consisting of cycles of repeated heating and cooling of reaction samples to amplify a single or a few copies of nucleotide fragments to generate thousands to millions of copies of a particular sequence within the nucleotide fragment.
Generally, PCR is carried out by a thermal cycler also known as a thermocycler, which alternatively heats and cools the reaction sample to a defined series of temperature steps. The reaction sample commonly includes nucleotide fragments, a pair of primers, a polymerase and deoxyribonucleotide triphates (dNTPs). In reaction, the nucleotide fragments, such as DNA fragments, serve as target templates. The primers are configured to anneal to the target template and are required for synthesis sequence initiation. The polymerase enzymatically assembles a new strand of nucleotide fragment from the synthesis material, i.e. dNTPs.
Each thermal cycler typically consists of three temperature steps: denaturation, annealing, and extension. Specifically, during denaturation, the thermal cycler heats the reaction samples to a first temperature to denature the nucleotide fragments from double strands to single strands. Annealing involves lowering the reaction sample to a second temperature to anneal the pair of primers to the nucleotide fragment. The polymerase binds to a primer-template hybrid, initiating sequence synthesis. Extension involves heating the reaction sample to a third temperature to enable the polymerase to have optimum activity. At this point, the polymerase synthesizes a new strand of nucleotide fragment complementary to the target sequence within the template, by adding the dNTPs. After a series of repeated cycles, amplification of the template achieves detectable magnitude.
Consequentially, optimization of PCR is time and efficiency-dependent vis-à-vis temperature control.
The conventional thermal cycler heats the reaction samples utilizing electrical resistive, Peltier, or radiation heating. However, such heating mechanisms usually employ heating elements with high specific heat capacity, and time-consuming heating and cooling sequences in achieving specific temperatures. In addition, the conventional thermal cycler consumes a lot of energy to cool down the temperature of the reaction sample. That is, energy is not used efficiently.